Tricks and tips to efficiently bleed Shimano brakes

Tricks and tips to efficiently bleed Shimano brakes


Shimano make some of the most well regarded and highly sought after brakes thanks to their excellent quality:price ratio.

These brakes, unlike almost all the other brands, use mineral oil. While it is not hygroscopic and doesn’t need to be replaced periodically like the DOT fluid, it does get degraded from use and overheating so it needs to be changed anyway.

To replace the oil and bleed Shimano brakes is pretty simple, but as often happens with older brakes, the standard procedure doesn’t work so well, resulting in spongy and weak braking.

Today we’ll discover how to optimally bleed our Shimano brakes, with a modified procedure which gives good results.

What do we need?

No specific tools are needed. You need a Shimano bleed kit with funnel and stopper…

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… a 7mm socket wrench, a 2,5mm and 3mm Allen key, and a plastic cup.

1) Preparation: First we have to get the brake ready for the bleed. Carefully remove the old pads.

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Place the specific yellow spacer between the pistons

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2) Lever and caliper positioning: place the lever so that the master cylinder is perfectly horizontal and higher than the caliper.

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2) Lever and caliper positioning: place the lever so that the master cylinder is perfectly horizontal and higher than the caliper.

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It’s better to bleed the caliper in vertical position, with the bleed port oriented upwards. This way the air naturally flows towards the hose and it is easier to remove it.

The front brake is already in the right position itself, to bleed the rear it’s better to remove the caliper and secure it in vertical position using a vise.

Get to work!

Now everything is ready for a proper bleed.

3) Preparation of the funnel: remove the port cap with the 3mm key and with a delicate touch (without damaging the plastic thread) screw on the funnel, filled in advance with approx. 1 inch of oil. Keep the funnel plugged with the included stopper.

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4) Preparation of the syringe: fill approximately 2/3 of the syringe with oil (full syringe to replace all the oil)  and install it on the caliper bleed port.

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5) Remove the air bubbles from the hose: remove the stopper from the funnel and open the caliper bleed port. Create a slight vacuum with the syringe to suck out all the air which is inside the hose or the connector (possibly even the caliper) and do not let it enter the system.

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WARNING: do not create too much vacuum when sucking the old oil, otherwise it will mix with the clean oil.

6) Oil replacement: Time to replace the old oil. Inject all the new oil which is inside the syringe into the system.

09…the old oil will flow out into the funnel.

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The oil coming out of the system is black like coal, a clear sign of its degradation.

PRO TIP: in order not to inject the old oil into the system again, it is better to suck it with another syringe, and replace it with clean oil.

7) Caliper bleed: close the bleed port on the caliper

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Remove the syringe from the hose and place the hose into a cup so that the oil doesn’t drip on the ground.

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Bleed the caliper:

  1. Open the port on the caliper
  2. Press the lever
  3. Close the port on the caliper
  4. Release the lever

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In the second phase the oil will come out from the hose, while in the fourth phase it will be sucked from the funnel.

PRO TIP: for a perfect bleed it is essential to be really firm during phase 2 and 4, pressing and releasing the lever quickly. This way, the instant pressure variation helps the bubbles to separate from the inside, resulting in a better bleed.

Repeat the “open-press-close-release” sequence a few times until no oil is left in the glass. Tap on the hose and the caliper with an allen key to help the air to come out. If air bubbles keep coming out of the caliper when the funnel of oil is almost empty, add some more oil and keep bleeding.

This phase requires a bit of patience.

WARNING: it takes some time for the air to get out, so usually at the beginning everything works perfectly, then after some cycles the bubbles start to come out. Don’t be fooled!

When no more air comes out, it is finished. Close the port firmly and remove the hose.

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Thoroughly clean any possible spilled oil with a rag and isopropyl alcohol.

8) Master cylinder bleed: after the caliper, let’s bleed the master cylinder. Press and release the lever quickly and firmly. Expect some bubbles to go out in the funnel.

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Tap on the hose while pressing/releasing the lever repeatedly, rotating it on the handlebar at various angles (upwards, downwards, horizontal). When no  more air comes out and the lever feels firm, the work is done.

9) Completion: plug the funnel with the supplied stopper and remove it, closing the port with a 3mm Allen key.

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Remove the yellow spacer from the caliper and reinstall the pads and rear wheel. Pump a few times (no worries if system feels empty) to reset the pistons and check that braking is efficient. Now we’re done!

WARNING: caliper centering is critical on Shimano brakes! If the caliper is not well centered on the disc, the brake becomes spongy. Before the bleed procedure, check that the disc is centered with respect to the pads.

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